Data from: Do the antipredator strategies of shared prey mediate intraguild predation and mesopredator suppression?

Understanding the conditions that facilitate top predator effects upon mesopredators and prey is critical for predicting where these effects will be significant. Intraguild predation (IGP) and the ecology of fear are hypotheses used to describe the effects of top predators upon mesopredators and prey species, but make different assumptions about organismal space use. The IGP hypothesis predicts that mesopredator resource acquisition and risk are positively correlated, creating a fitness deficit. But if shared prey also avoid a top predator, then mesopredators may not have to choose between risk and reward. Prey life history may be a critical predictor of how shared prey respond to predation and may mediate mesopredator suppression. We used hierarchical models of species distribution and abundance to test expectations of IGP using two separate triangular relationships between a large carnivore, smaller intraguild carnivore, and shared mammalian prey with different life histories. Following IGP, we expected that a larger carnivore would suppress a smaller carnivore if the shared prey species did not spatially avoid the large carnivore at broad scales. If prey were fearful over broad scales, we expected less evidence of mesopredator suppression. We tested these theoretical hypotheses using remote camera detections across a large spatial extent. Lagomorphs did not appear to avoid coyotes, and fox detection probability was lower as coyote abundance increased. In contrast, white-tailed deer appeared to avoid areas of increased wolf use, and coyote detection probability was not reduced at sites where wolves occurred. These findings suggest that mesopredator suppression by larger carnivores may depend upon the behavior of shared prey, specifically the spatial scale at which they perceive risk. We further discuss how extrinsic environmental factors may contribute to mesopredator suppression.

明晰能够促进顶级捕食者对中型捕食者与猎物产生调控效应的条件，对于预判此类效应的显著作用场景至关重要。集团内捕食（intraguild predation, IGP）与恐惧生态学（ecology of fear）是用于描述顶级捕食者对中型捕食者及猎物物种产生影响的两大假说，但二者对于生物体的空间利用模式做出了不同假设。集团内捕食假说（IGP）预测，中型捕食者的资源获取量与捕食风险呈正相关，进而引发适合度赤字。但若共享猎物同时也会规避顶级捕食者，则中型捕食者无需在捕食风险与收益之间做出权衡。猎物的生活史特征或许是预判共享猎物对捕食行为响应的关键因素，同时也可能介导中型捕食者所受的抑制效应。我们采用物种分布与丰度层级模型，针对大型食肉动物、小型集团内食肉动物以及具有不同生活史特征的共享哺乳类猎物之间的两类独立三角关系，检验了IGP假说的预期结论。依据IGP假说，若共享猎物在大空间尺度上未对大型食肉动物产生空间规避行为，则大型食肉动物会抑制小型食肉动物的种群发展；若猎物在大空间尺度上表现出恐惧规避行为，则中型捕食者受抑制的证据将会减弱。我们借助大空间范围内的远程相机监测数据对上述理论假说进行了检验。研究发现，兔形目动物并未表现出对郊狼的规避行为，且随着郊狼丰度提升，狐狸的物种检测概率随之降低。与之形成对比的是，白尾鹿会规避狼活动频率较高的区域，而在狼分布的样地中，郊狼的检测概率并未出现下降。上述研究结果表明，大型食肉动物对中型捕食者的抑制效应，可能取决于共享猎物的行为模式，具体而言取决于其感知捕食风险的空间尺度。我们还进一步探讨了外在环境因素如何对中型捕食者的抑制效应产生影响。